Related Field
The present invention relates to an arrangement and method for de-icing a structure. In particular the invention relates to an arrangement and method for de-icing a whole polymeric (fiber reinforced) or metallic wing or propeller. The invention also relates to a computer programme and a computer programme product. The invention also relates to a platform carrying the arrangement.
Description of Related Art
Aircrafts are continuously exposed to varying climatic condition and among the extremes situation is ice accretion one of the most threatening events. Ice accretion is known to cause serious perturbation to the flying conditions due to ice formations in aerodynamic surfaces of aircraft.
Ice accretion on aircrafts is a very complex physical process. The selection of an adequate ice rejection technique is thus a difficult task. The technique to be selected must be made compatible with a number of constrains comprising materials properties, fatigue, dynamic deformation while in flight, birds collision withstanding ability, repairing and servicing constrains, durability, etc. just to name a few. Therefore, any method to be considered has to be carefully analyzed in its total context to end up with technical conclusions of value.
One of the issues now upcoming is to be found on the growing need of fuel consumption reductions which in turn impose requirements of weight reduction and exceptional aerodynamic constrains, especially laminar air flow. This has been leading to the development of the Smart Fix-wings Aircraft concept where the wings are thought to be made of light weight fiber reinforced epoxy. The removal of ice can be accomplished either by providing melting heat or mechanical stresses to the skin just to surpass adhesion forces of the accreted ice layer. Heat however is known to demand too much power, and in the case of epoxy based material, high temperature is an ageing factor that should be avoided. Mechanical stresses on the other hand should be impulsive to minimize the energy consumption and to accomplish ice cracking while destroying the ice surface adhesion. The accreted ice will then be removed mainly due to the drag forces of the air. Therefore, actuators able to accomplish wing skin surface displacements through the action of impulsive forces are highly interesting.
U.S. Pat. No. 5,584,450 depicts an electro-expulsive de-icing system for attachment to an airfoil which is comprised of a plurality of electro-expulsive elements separated by a dielectric filler regions all of which are disposed between a top dielectric layer and a bottom dielectric layer. A contiguous top skin layer covers the entire de-icing apparatus.
U.S. Pat. No. 5,129,598 depicts an attachable electro-impulse de-icer for de-icing an aircraft structural member including an inductor coil disposed in proximity with the outer surface of the structural member. The coil is supported by a flexible ice-accumulating support member that permits the coil to move relative to the structural member. The coil and the support member may be formed in an integral construction that can be attached to the leading edge of the structural member. The coil and the support member are rapidly displaced away from the structural member upon passing a short-duration, high current pulse through the coil.
Known ice rejection methods are mostly conceived for metallic skin materials and are mostly inductive or thermal (heating). There are even methods that accomplish deicing through total deformation (inflatable layers, etc.).
Known drawbacks of some of the methods are related to the fact that those ice rejection devices introduce significant local perturbation to air flow. Since laminar flow, particularly at wing surfaces, is a much wanted feature from the view point of aerodynamic considerations, any protrusion to the surfaces is not acceptable.
Another drawback of known deicing methods is to be found in the melting of the interlayer of ice and wings which may lead to a gliding effect of the accreted ice pushing it back of simply generating water that flows back and risk to be frozen at the ailerons of aircraft wings.